        body {
            font-family: 'Microsoft YaHei', Arial, sans-serif;
            margin: 0;
            padding: 0;
            background-color: #f5f5f5;
            color: #333;
        }
        .container {
            display: flex;
            max-width: 1200px;
            margin: 20px auto;
            background-color: #fff;
            box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
            border-radius: 5px;
            overflow: hidden;
        }
        .sidebar {
            width: 250px;
            background-color: #2c3e50;
            color: #fff;
            padding: 20px;
            box-sizing: border-box;
        }
        .main-content {
            flex: 1;
            padding: 20px;
            box-sizing: border-box;
        }
        .question-nav {
            margin-bottom: 30px;
        }
        .nav-section {
            margin-bottom: 20px;
        }
        .nav-title {
            font-weight: bold;
            margin-bottom: 10px;
            font-size: 16px;
            border-bottom: 1px solid #34495e;
            padding-bottom: 5px;
        }
        .question-numbers {
            display: flex;
            flex-wrap: wrap;
            gap: 8px;
        }
        .question-number {
            width: 30px;
            height: 30px;
            line-height: 30px;
            text-align: center;
            background-color: #34495e;
            border-radius: 50%;
            cursor: pointer;
            transition: all 0.3s;
        }
        .question-number:hover {
            background-color: #1abc9c;
        }
        .question-number.answered {
            background-color: #3498db;
        }
        .question-number.current {
            background-color: #e74c3c;
        }
        .submit-btn {
            display: block;
            width: 100%;
            padding: 10px;
            background-color: #e74c3c;
            color: white;
            border: none;
            border-radius: 5px;
            font-size: 16px;
            cursor: pointer;
            margin-top: 20px;
            transition: background-color 0.3s;
        }
        .submit-btn:hover {
            background-color: #c0392b;
        }
        .question-container {
            min-height: 400px;
            padding: 20px;
            background-color: #fff;
            border-radius: 5px;
            box-shadow: 0 0 5px rgba(0, 0, 0, 0.05);
        }
        .question-title {
            font-size: 18px;
            font-weight: bold;
            margin-bottom: 15px;
            color: #2c3e50;
        }
        .question-content {
            margin-bottom: 20px;
            line-height: 1.6;
        }
        .options {
            margin-left: 20px;
        }
        .option {
            margin-bottom: 10px;
        }
        .code-editor {
            width: 100%;
            height: 200px;
            border: 1px solid #ddd;
            font-family: 'Courier New', monospace;
            padding: 10px;
            box-sizing: border-box;
            margin-top: 10px;
        }
        .navigation-buttons {
            display: flex;
            justify-content: space-between;
            margin-top: 20px;
        }
        .nav-btn {
            padding: 8px 15px;
            background-color: #3498db;
            color: white;
            border: none;
            border-radius: 5px;
            cursor: pointer;
            transition: background-color 0.3s;
        }
        .nav-btn:hover {
            background-color: #2980b9;
        }
        .nav-btn:disabled {
            background-color: #95a5a6;
            cursor: not-allowed;
        }
        .timer {
            text-align: right;
            font-size: 18px;
            margin-bottom: 20px;
            color: #e74c3c;
        }
